Such a data service has been widely provided that servers and clients linked to one another via a network communicate with one another and that contents stored in server apparatuses are download into client terminals (receiving apparatuses) and used. Especially, because of the current widespread use of broadband networks, such a mechanism is being put into place that even a content having a large capacity of transmission (e.g., a digital video image) is processed. According to this mechanism, a plurality of AV contents are stored in a server, are downloaded or streamed at a client's request, and are reproduced at a client terminal.
FIG. 14 is a diagram schematically showing a conventional video delivery system 1300 in which a server apparatus 1301 is linked to receiving apparatuses 1302 via a network and in which the server apparatus 1301 delivers an AV content to each of the receiving apparatuses 1302. This is a so-called networked video-on-demand system. Further, there have been increasingly various kinds of similar system and service that do not use a network. Examples of such a system and service include a server-type broadcasting system and service. According to the server-type broadcasting system and service, a content stored in a receiving apparatus by using a broadcast wave is viewed.
FIG. 15 shows an embodiment of the AV content to be treated in the video delivery system 1300. The AV content includes a playlist and clip data. Note that FIG. 15 is also an explanatory diagram of the present invention.
The AV content shown in FIG. 15 includes (i) a plurality of files (clip data 1402) containing actual data such as video images and sounds and (ii) a file (playlist 1401) indicating a reproduction procedure in which the actual data are reproduced (as well as places where the actual data are reproduced). That is, the playlist 1401 and the plurality of clip data 1402 are collectively treated as the single AV content 1400. How the playlist 1401, the clip data 1402, and the AV content 1400 constituted thereby are treated is fully described in Japanese Unexamined Patent Application No. 56651/2002 (Tokukai 2002-56651; published on Feb. 22, 2002).
Generally, in the video delivery system 1300, a plurality (large number) of receiving apparatuses 1302 are connected to a single server apparatus 1301.
Moreover, in the video delivery system 1300, when the AV content 1400 is allowed to be downloaded into the receiving apparatuses 1302 in different procedures, it becomes difficult to manage which files (clip data 1402) resident on the server apparatus 1301 can be respectively downloaded next into the receiving apparatuses 1302. Examples of a file that can be downloaded by a receiving apparatus 1302 include (i) a file yet to be acquired by the receiving apparatus 1302 and (ii) a file which has already been downloaded by the receiving apparatus 1302 and which needs rewrites to match new content. Therefore, in order to find a downloadable file, it is necessary to find (files constituting) an AV content already acquired by the receiving apparatus 1302.
Especially, in cases where an update is performed by sequentially downloading the constituent files, i.e., the clip data 1402 of the AV content 1400, an instruction to reproduce the playlist 1401 referring to the clip data 1402 may be given when new clip data 1402 have not been downloaded (are being downloaded) or when the clip data have failed to be completely downloaded. This causes such a problem that reproduction different from that originally expected is performed by referring to another file that was downloaded in the past.
The present invention has been made in view of the foregoing problems, and it is an object of the present invention to provide (i) a data management system in which a server apparatus stores a plurality of data files and appropriately delivers the plurality of data files to a receiving apparatus and in which data management can be effectively preformed in the receiving apparatus, (ii) a server apparatus and a receiving apparatus together constituting the data management system, (iii) a data management method, (iv) a control program, and (v) a computer-readable recording medium in which the control program is recorded.